This invention relates to an improved system and method for restraining cargo during transportation. More particularly, this invention relates to a novel system and method for securing and restraining undesired movement of drums, boxes, rigid and flexible containers, palletized or not palletized, within the interior of a truck body, a railroad car, an intermodal container, and the like. Moreover this invention relates to a system and method of enhanced securement strength and reduction of load shifting during transport.
In the United States most overland shipping is accomplished using either a tractor/trailer truck combination, often referred to descriptively as an eighteen wheeler, or via railroad boxcars and/or truck trailers mounted on flatcars. Truck trailers are typically forty five, forty eight or fifty three feet in length and are often loaded with cargo in containment enclosures such as 55 gallon closed head drums, super sacks or plastic reinforced bags, plastic wrapped bundles, cased goods, metal coils, specialty heavy paper rolls, plastic or metal containers mounted on pallets, and the like. Although each containment enclosure or bundle may be quite heavy and stationary at rest, the mass of a transport load can produce considerable momentum force as a truck or rail car is placed in motion.
Rail cars may be made up by a coupling or humping process within a switching yard. When a railroad car is rolled into a stationary string of cars, the impact causes the car couplings to lock together with a jolt. This impact can apply a significant force to cargo within the rail car. Moreover, during transport, railway cars are subject to braking forces, run-in and run-out coupler impact over grades, rail vibration, dips in the track, and swaying. In a similar manner trucks are subject to stopping and starting forces, emergency braking, bumps and swaying from uneven road beds, centrifugal forces on curves, vibration, etc. which tend to shift loads.
In addition to the above discussed overland shipping, most shipments for export, both in the United States and abroad, are placed into intermodal containers. These containers have standardized dimensions of twenty or forty feet in length and are fabricated with steel, corrugated sidewalls which are structurally self-supporting and rugged. Several intermodal containers may be stacked on top of each other for transport by sea, rail, or road. Within the containers, drums, boxes, etc. hold actual product as noted above.
The cargo of these intermodal containers experience various forces throughout the course of transport as noted above in connection with overland transport, such as, acceleration, centrifugal loads, braking, vibration, etc. as noted above. In addition, intermodal containers, when loaded onto ships for ocean transport, are subjected to wave forces including: yaw, pitch, heave, sway, and surge. Each of these forces has the potential to impart a substantial force on the contents within an intermodal container. In this, when a container changes direction or speed, cargo within the container tends to continue along the previously existing path until it contacts an interior wall of the container. Without some type of restraint and/or cushioning system, the cargo builds up considerable momentum, independent of the container. The amount of momentum is equal to the mass of a load multiplied by its velocity. In the case of large cargo loads, even a small change in velocity or direction can generate substantial forces.
When cargo contacts the interior walls or doors of a container, the force necessary to reduce its momentum to zero must be absorbed by the goods and/or the container. Such forces can result in damage to the cargo, damage to the interior walls or doors of the container, damage to the cargo packing, and may create dangerous leaks if the cargo is a hazardous material. Accordingly, it is undesirable to permit cargo to gain any momentum independent of a container during transport. This is accomplished by restraining the cargo within the container so that the cargo and the container are essentially united and operationally function as one object during transport.
In order to secure the load during transport and minimize undesired shifting and damage the load containment enclosures are often secured to the floor and/or sides of the trailer or boxcar by specially fabricated wood framing, floor blocking, rubber mats, steel strapping, heavy air bags, etc. Each of these previously known systems for securement have limitations associated with construction cost, lack of strength sufficient to secure dense loads, etc. Moreover, although rear doors of a trailer may be relied on to at least partially secure non-hazardous materials such as food-stuffs, tissue or soft paper products, furniture, appliances, etc., for hazardous materials, and many other types of loads, the rear doors of a container may not be used to even partially secure a load. In fact, in order to comply with Department of Transportation Regulations and Bureau of Explosives, hazardous materials are not even permitted to come in contact with rear doors during an impact.
Still further in some instances a trailer or boxcar may be used for shipping where only a partial load is carried. Moreover, a partial load might be positioned within a center location of a trailer. In this instance it may be impractical to construct wooden front and rear dunnage sufficient to secure a load where the front of the trailer is not utilized.
In the past, various dunnage materials have been utilized within trailers and/or intermodal containers to eliminate unwanted movement or shifting of a load during transport. The drums, boxes, or other containers have been restrained in several different ways. Primarily, cargo was stabilized by a method of load-locking and lumber bracing. This system involves strategically placing lumber between a load face and the rear doors of a container. This, however, can be a costly, time consuming, and generally inefficient means of securing a load. In this, the blocking process requires carpenters and is often outsourced to contractors. Moreover, wooden barriers can be time consuming to install. Further wood bracing can be somewhat brittle and subject to failure as a result of an abrupt impact.
In addition to the above, conventional methods of load-blocking with lumber bracing simply can not perform some tasks. For example, the most efficient means of filling an intermodal container is eighty, fifty-five gallon drums, double stacked in a twenty-foot long container. However, if eighty barrels are loaded there are only approximately four inches between the load face and rear doors of the container. Four inches is not enough space to put sufficient lumber to brace a load of eighty drums adequately. Consequently, when wood bracing is utilized as a system of restraint, shippers are forced to ship containers that are not filled to capacity. This reduces transport efficiency and increases transportation costs. Moreover, some types of wood, such as conifer woods which include evergreen, cone-bearing trees, such as pine, spruce, hemlock, or fir, are not acceptable to cross international boundaries without certification of special fumigation or heat treatment processing of conifer wood dunnage to prevent importation of pests. In this the International Plant Protection Convention (“IPPC”) has issued “Guidelines for Regulating Wood Packaging Material in International Trade” having specific sections, requirements and limitations with respect to wood dunnage that has been accepted by numerous countries including the United States.
The Department of Transportation has established a standard to determine if a particular restraint system is capable of adequately securing hazardous cargo. In certain instances, conventional load-locking and lumber bracing has not received approval to ship hazardous cargo.
Other known means of restraint such as ropes, metal or plastic straps or stands and the like appearing in the past have tended to exhibit impaired performance and are often not functionally suitable to restrain loads under even moderate conditions. Consequently, a need exists for securing lading in truck trailers, boxcars, and intermodal containers that is functionally effective, cost-efficient, labor-efficient, and able to comply with Department of Transportation, Bureau of Explosives and/or the Association of American Railroads regulations. Still further a need exists for securement systems that have enhanced strength characteristics and limit lading travel within a container.
At least one method and apparatus for restraining cargo movement which overcomes some of the foregoing limitations is disclosed in U.S. Pat. No. 4,264,251, of common assignment with the subject application. The invention disclosed in that patent comprises sealing strips that are adhered to opposing sidewalls of a container, a strip of bracing material, and a joining mechanism are used to bind the ends of the strips together into a secure and taut restraint.
In the '251 patent, flexible securement strips are applied in a manner similar to hanging wallpaper, wherein an adhesive is applied onto a surface within a trailer where adhesion is desired. Then a retaining strip is applied to the adhesive. In addition to this requirement of a separate adhesive, systems appearing in the past sometimes encountered problems associated with weakness at the joints. At the juncture where the strips came together, an opportunity existed for slippage of the joined panels. Moreover, intermodal containers have corrugated walls as noted above. These corrugations make applying a restraining strip to a separate adhesive, which may not have an even application, substantially more difficult.
In addition to the restraining system disclosed in U.S. Pat. No. 4,264,251 other systems have been developed that provide enhanced operating characteristics and advantages, as discussed in the above identified U.S. Pat. Nos. 6,089,802; 6,227,779 and 6,607,337 all of common inventorship and assignment as the subject application. The disclosures of these prior four patents, of common assignment as the subject application, are hereby incorporated by reference as though set forth at length.
Further to these prior systems of securing lading in truck trailers, railroad cars, and intermodal containers increasing attention has been placed on securing heavier and denser loads, including hazardous materials, without abandoning the advantages achieved by previously known commercial systems. Moreover, there is interest in decreasing the elastic and/or plastic elongation permitted with prior securing systems so that hazardous materials can be transported with enhanced efficiency. In this regard it would be desirable to utilize eighty, fifty five gallon, drums within a conventional intermodal container. In this arrangement four steel drums need to be positioned next adjacent to the rear door of an intermodal container. In the past, issues have existed with respect to unacceptable travel of loads which may even come into contact with rear doors of the container during impact. As noted above, for hazardous loads, load contact with the rear doors is not acceptable by HazMat regulations.
In addition to the above, other restraining systems known in the past required multiple elements which were cumbersome to store, were arduous to install, and often required a degree of skilled labor. Systems using straps, nails, anchors, or bolts all require substantial storage space even when not in use. Furthermore, such systems increase the safety risk to the workers restraining the cargo. Still further such systems have often been unable to satisfy safety and travel limits imposed by regulatory bodies in various countries.
In addition to the above concerns, systems and procedures used in the past relying on accessories located within the cargo container often were not able to secure a partial load. That is, if the load does not extend to the front or rear of the container, such as a centrally located load, the necessary anchors may not be available in an area where they can be effectively used.
The problems suggested in the preceding are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness of cargo restraining systems known in the past. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that cargo-restraining systems appearing in the past will admit to worthwhile improvement.